Creep resistant Nb-silicide based multiphase composites

ABSTRACT

A niobium-based silicide composite exhibiting creep resistance at temperatures equal to or greater than 1150° C. The niobium-based silicide composite comprises at least silicon (Si), hafnium (Hf), titanium (Ti), and niobium (Nb). A concentration ratio of Nb:(Hf+Ti) is equal to or greater than about 1.4. The niobium-based silicide composite exhibits a creep rate less than about 5x10-8s-1 at temperatures up to about 1200° C. and at a stress of about 200 MPa.

This invention was made with Government support under Contract No.F49620-96-C-0022 awarded by the Department of Defense—United States AirForce and therefore, the Government has certain rights in the invention.

BACKGROUND OF THE INVENTION

The invention relates to multiphase Nb-silicide in-situ compositeshaving improved creep performance. In particular, the invention relatesto multiphase Nb-silicide based composites having a certain ratio ofniobium (Nb), hafnium (Hf), and titanium (Ti).

Traditionally, turbine components have been often formed fromnickel-(Ni) based superalloys materials. These Ni-based superalloys havebeen used for turbines and turbine components, such as but not limitedto, jet engine turbines, land-based turbines, marine-based turbines, andother high temperature turbine environments. The applications of theseNi-based superalloy turbine components may be limited by the hightemperatures associated with turbine component operations. Surfacetemperatures during operation of turbine components can approachtemperatures up to and above 1150° C., which are approximately 85% ofthe melting temperatures of the Ni-based superalloy. Therefore, thesetemperatures can limit the applications of Ni-based superalloys as thehigh temperatures may adversely influence the Ni-based superalloy'sstrength, oxidation resistance, and creep resistance. Further, otherintrinsic Ni-based superalloy properties at these high temperatures,such as but not limited to, fracture toughness, high-temperaturestrength, oxidation resistance, and other mechanical properties, mayprevent further applications.

In order to overcome the above-noted deficiencies of the Ni-basedsuperalloys, niobium-(Nb) and molybdenum-(Mo) modified Nb-silicide basedcomposite materials have been investigated for turbine componentapplications. Niobium has been used to form refractory metalintermetallic composites (hereinafter referred to as “RMIC”s), whichinclude, but are not limited to, Nb-based refractory metal intermetalliccomposites. RMICs, such as but not limited to Nb-silicide basedcomposites, possess potentially high operating temperatures, forexample, but not limited to, those temperatures encountered in turbinecomponent applications. These RMICs have higher melting temperaturesthat Ni-based superalloys, and thus may find beneficial applications inturbine components. For example, some RMICs may have meltingtemperatures in excess of 1700° C., which would be desirable in aturbine component application. See M. R. Jackson et al.,“High-Temperature Refractory Metal-Intermetallic Composites”, Journal ofMaterials, January 1996 (pp. 39-44).

RMIC mechanical properties, such as, fracture toughness,high-temperature strength, and oxidation resistance are also enhancedcompared to Ni-based superalloys. However, Nb-based refractory metalintermetallic composites may possess poor creep resistance at elevatedtemperatures, which would be undesirable in turbine components. Thiscreep performance may be due to the existence of an additional hP16hexagonal phase, which is present in Nb-based composites.

Thus, there is a need for improved high temperature alloys for turbinecomponent applications. Therefore, another need exists to provide aNb-based material for high temperature applications, in which theNb-based material can find use in high temperature applications withenhanced creep resistance.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention provides a multiphase niobium-basedsilicide composite that exhibits creep resistance at temperatures equalto or greater than 1150° C. The niobium-based silicide compositecomprises at least silicon (Si) hafnium (Hf), titanium (Ti), and niobium(Nb). The concentration ratio of Nb:(Hf+Ti) is equal to or greater thanabout 1.4 and the niobium-based silicide composite comprises at leastsilicon (Si), hafnium (Hf), titanium (Ti), and niobium (Nb), wherein aconcentration ratio of Nb:(Hf+Ti) is equal to or greater than about 1.4and the niobium-based silicide composite exhibits a creep rate less thanabout 5×10⁻⁸s⁻¹ at temperatures up to about 1200° C. and at a stress ofabout 200 MPa.

Another aspect of the invention provides a multiphase niobium-basedsilicide composite that exhibits high temperature creep resistance attemperatures up to about 1200° C. The niobium-based silicide compositecomprises, in atomic percent, up to about 25% titanium (Ti), silicon(Si) in a range from about 10% to about 22%, at least about 4% hafnium(Hf), and a balance niobium (Nb).

A further aspect of the invention provides a method for forming amultiphase niobium-based silicide composite. The composite exhibitscreep resistance at elevated temperatures. The method of forming thecomposite comprises providing silicon (Si), hafnium (Hf), titanium (Ti)and niobium (Nb), and optionally tantalum (Ta), germanium (Ge), iron(Fe), boron (B), molybdenum (Mo), aluminum (Al), chromium (Cr), andtungsten (W). A ratio of Nb:(Hf+Ti) is equal to or greater than about1.4.

Another aspect of the invention provides a turbine component comprising,in atomic percent, 7.5% hafnium (Hf), 16% silicon (Si), 21% titanium(Ti), and a balance niobium (Nb).

Still another aspect of the invention provides a turbine componentcomprising, in atomic percent, 8% hafnium (Hf), 16% silicon (Si), 21%titanium (Ti), and a balance niobium (Nb).

In a further aspect of the invention provides a turbine componentcomprising, in atomic percent, 3% molybdenum (Mo), 8% hafnium (Hf), 16%silicon (Si), 25% titanium (Ti), and a balance niobium (Nb).

An additional aspect of the invention provides a turbine component, inatomic percent, 9% molybdenum (Mo), 8% hafnium (Hf), 16% silicon (Si),25% titanium (Ti), and a balance niobium (Nb).

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will become apparent fromthe following description of the invention, which refers to theaccompanying drawings, wherein:

FIG. 1 illustrates the microstructure of a composite directionallysolidified from a quaternary Nb—Hf—Ti—Si alloy having a Nb: (Hf+Ti)ratio greater than about 1.4;

FIG. 2 is a backscatter electron image (BEI) of a transverse section ofa Nb—9Mo—22Ti—8Hf—16Si alloy with a Nb:(Hf+Ti) ratio of about 1.5;

FIG. 3 is a plot of creep rate as a function of the percentage ofsilicon in an alloy composition, as embodied by the invention; and

FIGS. 4-6 are plots of creep rate as a function of the Nb:(Hf+Ti) ratioin a Nb—16Si alloy of a series of Hf and Ti concentrations in alloys, asembodied by the invention, at a plurality of stresses.

DETAILED DESCRIPTION OF THE INVENTION

Niobium (Nb)-based refractory metal-intermetallic composites, asembodied by the invention, can be used in high temperature applications.These high temperature applications comprise, but are not limited to,applications in turbines, such as in components of aeronauticalturbines, land-based turbines, jet engine turbines, marine turbines, andsimilar turbines (hereafter referred to as “turbine components”). Theturbine component may comprise, but is not limited to, a vane, blade,bucket, and stator. The following description of the invention, willrefer to a turbine component in general. This description is notintended to limit the invention in any manner, and the scope of theinvention comprises any turbine component.

Multiphase Nb-silicide based composites are typically developed frombinary alloys, which include at least niobium (Nb) and silicon (Si).Nb-silicide based composites can enhance high-temperature oxidationperformance and fracture toughness in a turbine component. Further, theNb-silicide based composite can provide the turbine component sufficienthigh-temperature strength and stiffness, for applications attemperatures equal to and above about 1150° C., which are temperaturesoften encountered in turbine component applications. The term multiphasemeans that the composite comprises at least two or more phases. Themultiphase Nb-silicide based composite, as embodied by the invention,will be referred to hereinafter as a “Nb-silicide based composite”.

A Nb-silicide based composite, as embodied by the invention, cancomprise other constituents to modify various mechanical and thermalproperties. The Nb-silicide based composite can be modified by adding atleast one of: hafnium (Hf), titanium (Ti), molybdenum (Mo), boron (B),geranium (Ge), iron (Fe), tungsten (W), chromium (Cr), tantalum (Ta),tin (Sn), and aluminum (Al) (hereinafter collectively referred to as“modifiers”) to the Nb-silicide based composite. These modifiers canenhance mechanical and thermal properties of the Nb-silicide basedcomposite at high-temperatures, such as, but not limited to, oxidationresistance, room temperature toughness, and strength. Further, theNb-silicide based composite, as embodied by the invention, can compriseat least one of niobium silicides, such as, but not limited to, Nb₃Siand Nb₅Si₃, each of which can be toughened by adding niobium (Nb).

The Nb-silicide based composite, as embodied by the invention, comprisesamounts of Ti and Hf that are controlled to maintain high-temperatureoperational creep performance of the Nb-silicide based composite. Forexample, a Nb:(Ti+Hf) concentration ratio is in a range from about 1.4to about 2.5, and often the Nb:(Ti+Hf) concentration ratio is about 1.4,to allow for desirable creep performances at creep rates of about 140MPa and above. Further, Nb amount in the Nb-silicide based composite canbe maintained at a certain level, thus maintaining the high-temperaturecreep performance in the Nb-silicide based composite, as embodied by theinvention. Although lower Nb:(Hf+Ti) concentration ratios may bedesirable for oxidation resistance characteristics of the Nb-silicidebased composite, lower concentration s of Nb:(Hf+Ti) may have an adverseeffect on creep resistance.

The amounts of the modifiers of the Nb-silicide based composite, asembodied by the invention, can be provided within certain ranges. Forexample, the niobium-based silicide composite may comprise, in atomicpercent, up to about 10% tantalum (Ta), hafnium (Hf) in a range fromabout 2% to about 8% such as but not limited to about 4%, silicon in arange from about 10% to about 22%, up to 25% titanium (Ti), up to about10% germanium (Ge), up to about 5% tin (Sn), up to about 6% iron (Fe),up to about 8% boron (H), up to about 3% molybdenum (Mo), up to about 5%aluminum (Al), and one of chromium (Cr) up to about 15% and tungsten (W)up to about 5%, silicon (Si) in a range from about 10% to about 22%, and a balance niobium (Nb). The term “up to” means that the amount of themodifier may be zero, in which none of that modifier is provided.Further, the term “up to” means that the amount of the modifier may be atrace amount, in which small amounts of the modifier are provided, forexample, amounts less than or equal to about 1% by atomic. In thedescription of the invention, the values are provided in approximateterms, unless specifically indicated.

The Nb-silicide based composites, as embodied by the invention, wereinvestigated for their material characteristics, including but notlimited to, creep resistance and creep rates. The investigation isconducted by preparing Nb-silicide based composite samples (hereinafter“sample”) using cold crucible Czochrolski directional solidification,which followed triple melting of high purity elemental starting charges(hereinafter “starting charges”). The term “high purity” means that thestarting charges were greater than about 99.99% pure. The startingcharges were induction melted in a segmented water-cooled coppercrucible. A Nb—16Si composition was used as a base binary alloycomposition from which the higher order alloys were derived, asdiscussed hereinafter.

Various Nb-silicide based composite samples were prepared to determinetheir material characteristics. All concentrations are given inapproximate atom percent unless otherwise specified. Some data for theNb-silicide based composite samples are set forth in Table 1, whichincludes creep rates.

TABLE 1 Major Constituent Nb (Hf + Ti) 140 MPa Creep 210 MPa 280 MPaComposition Phases Ratio Rate (s⁻¹) Creep Rate(s⁻¹) Creep Rate(s⁻¹)Nb-16Si (Nb), Nb₃Si — 1.5 × 10⁻⁸ 4.9 × 10⁻⁸ Failed Nb-7.5Hf- (Nb), Nb₃Si10.2 2.3 × 10⁻⁸ 4.0 × 10⁻⁸ 4.8 × 10⁻⁸ 16Si Nb-7.5Hf- (Nb), Nb₃Si 1.952.1 × 10⁻⁸ 3.2 × 10⁻⁸ 1.2 × 10⁻⁷ 21Ti-16Si Nb-12.5Hf- (Nb), Nb₃Si 1.515.5 × 10⁻⁸ 4.8 × 10⁻⁶ Failed 21Ti-16Si Nb-12.5Hf- (Nb), Nb₃Si 0.85 3.8 ×10⁻⁵ Failed 33Ti-16Si (Ti, Hf)₅Si₃

The compression and tension creep tests that resulted in the data inTable 1 were performed at temperatures of about 1200° C. Further, thecompression and tension creep tests were conducted at stress levelranges listed in Table 1. The Nb-silicide based composites were formedinto cylindrical samples, which were about 7.6 mm in diameter and about15.3 mm in length. The Nb-silicide based composite samples weremachined, for example by EDM and then centerless ground, to their finaldimensions.

In each of the investigative tests, the sample was placed between two18.7 mm diameter silicon nitride platens, which prevented breakage ofgraphite rams used to apply forces thereto. Additionally, essentiallypure niobium foil was placed at interfaces between the platens andsample to prevent sample contamination or reaction with the platens. Thecreep rate tests included placing a sample between the platens.

A furnace was heated to a desired temperature, the sample was thenloaded to the first stress level of 35 MPa, and held at that level for24 hours. The creep rate was determined from the slope of thestrain-time data. At the end of 24 hours, the sample dimensions weredetermined. The load was increased to the next desired stress level.

Table 1 shows the creep rates of binary Nb—16Si, ternary Nb—7.5Hf—16Si,and a range of quaternary Nb—Hf—Ti—Si alloys to illustrate allowable Hfand Ti concentrations for a Nb-silicide based composite, as embodied bythe invention. The compositions were modified by varying the Nb:(Hf+Ti)ratio. The secondary creep rates were essentially similar, for examplethe rates at about 1200° C. and at stresses up to about 210 MPa wereessentially similar (except for Nb—12.5Hf—33Ti—16Si). However, at 280MPa the creep rate of the binary and the quaternary Nb—12.5Hf—21Ti—16Sialloy led to the failure of the samples, while the Nb—7.5Hf—16Si had acreep rate less than about 5.0×10⁻⁸s⁻¹.

The data of Table 1 indicates that addition of Hf at low levels canprovide reduced creep rates and increased creep resistance. Also, thedata indicates that there are Ti and Hf concentrations above which creepperformance of the Nb-silicide based composite is degraded. Theseconcentration levels can be described by the Nb:(Hf+Ti) concentrationratio. The data in Table 1 indicates that above specific Ti and Hfconcentrations, a creep rate may exceed a desired creep rate of3×10⁻⁸s⁻¹, which corresponds to a creep strain of 1% in 100 hours withminimal primary creep.

Further, with higher Ti concentrations, such as in Nb—7.5Hf—33Ti—16Si atstress levels of 140 MPa and above, creep rates are all higher than adesired creep rate, which is less than 3×10⁻⁸s⁻¹. Similarly, higher Hfconcentrations, such as in Nb—12.5Hf—21Ti—16Si at creep rates of 140 MPaand above, the creep rates are all higher than the desired creep rate.With high Hf and Ti concentrations, such as in Nb—12.5Hf—33Ti—16Si atcreep rates of 140 MPa and above, the creep rates are higher than therequired creep rates. Furthermore, while higher Ti concentrations may bedesirable for oxidation resistance, the higher Ti concentrations may bedeleterious to creep performance, thus a balance of the materialcharacteristics and Ti concentration is desirable. At Nb:(Hf+Ti)concentration ratios less than 1.5, the creep performance is degradedbeyond acceptable levels for stresses of 140 MPa and above.

Analysis of a sample's microstructural constituent phases in which thesample comprises high Hf and Ti concentrations indicates that atNb:(Hf+Ti) concentration ratios less than about 1, a third phase, thehexagonal phase, hP16, is stabilized in these Nb-silicide basedcomposites. The hP16 is a hexagonal close packed complex crystalstructure with 16 atoms per unit cell. The presence of the hP16 phasecan be estimated by metallographic methods using sections of the sample.It is believed that the hP16 hexagonal phase can lead to the results aslisted in Table 1.

FIG. 1 illustrates a microstructure of a Nb-silicide based compositedirectionally solidified from a quaternary Nb—Hf—Ti—Si alloy with aNb:(Hf+Ti) concentration ratio greater than 1.4. These quaternary alloyNb-silicide based composites comprising Nb:(Hf+Ti) concentration ratiosgreater than 1.4 possess only Nb and Nb₃Si phases, as shown in FIG. 1.In FIG. 1, the dark area is Nb and the light area is Nb₃Si. It appearsthat if the hP16 phase exists at volume fractions greater thanapproximately 5%, the creep performance of the Nb-silicide basedcomposite is substantially degraded, for example as observed inNb—12.5Hf—33Ti—16Si. Thus, for hypoeutectic Nb-Si alloys, the ratioabove which the Nb: (Hf+Ti) concentration ratio should be maintained fordesirable creep performance is approximately 1.4.

Nb-silicide based composites of quaternary Nb—Hf—Ti—Si were modifiedwith molybdenum to further illustrate Nb-silicide based compositecharacteristics. Table 2 lists data including creep rates of theMo-modified Nb-silicide based composite alloys with Nb-silicide basedcomposites including a base Nb—16Si, Nb—7.5Hf—16Si, and Nb—8Hf—25Ti—16Sicomposites at 1200° C. The samples listed in Table 2 were prepared in amanner similar to those summarized in Table 1, in which the Nb-silicidebased composite samples were directionally solidified and compressioncreep tested.

TABLE 2 Major NB: Constituent (Hf + Ti) 70 MPa 140 MPa 210 MPaComposition Phases Ratio Creep Rate(s⁻¹) Creep Rate(s⁻¹) Creep Rate(s⁻¹)Nb-16Si (Nb), Nb₃Si — 1.7 × 10⁻⁹ 1.5 × 10⁻⁸ 4.9 × 10⁻⁸ Nb-7.5Hf-16Si(Nb), Nb₃Si 10.2 — 2.3 × 10⁻⁸ 4.0 × 10⁻⁸ Nb-8Hf-25Ti- (Nb), Nb₃Si 1.566.3 × 10⁻⁹ 1.2 × 10⁻⁸ 8.0 × 10⁻⁸ 16Si Nb-3Mo-8Hf- (Nb), Nb₃Si 1.46 1.4 ×10⁻⁸ 2.5 × 10⁻⁸ 6.4 × 10⁻⁸ 25Ti- 16Si Nb-9Mo-8Hf- (Nb), Nb₃Si 1.27 2.6 ×10⁻⁸ 2.2 × 10⁻⁷ 4.5 × 10⁻⁶ 25Ti-16Si (Ti,Hf)₅Si₃ Nb-8Hf-24Ti- (Nb),Nb₃Si 1.50 9.1 × 10⁻⁸ Failed — 2A1-2Cr-16Si (Ti,Hf)₅Si₃

The results of Table 2 indicate that creep rates increase with anincreasing Mo concentration. At a creep rate of about 280 MPa, theMo-modified samples failed without establishing a steady state. TheNb:(Hf+Ti) concentration ratio for the Nb-silicide based composite alloycomprising 9Mo was about 1.27. The creep rate change can be associatedwith a change in both the constituent phases and phase morphology in theNb-silicide based composites.

For example, FIG. 2 is a backscatter electron image (BEI) of atransverse section of a Nb—9Mo—25Ti—8Hf—16Si alloy, as embodied by theinvention. The Mo-modified Nb-silicide based composite possesses amicrostructure including fine-scale two-phase eutectic cells ofbody-centered cubic (bcc) (Nb), and hPl6 ((Ti, Hf)₅Si₃) type phases. TheMo-modified Nb-silicide based composite with 3% Mo possesses amicrostructure with large-scale bcc (Nb), and Nb₃Si, type phases.

Similar Nb-silicide based composite behavior is also evident inNb—8Hf—24Ti—2Al—2Cr—16Si that has a Nb:(Hf+Ti) concentration ratio ofabout 1.5. In this Nb-silicide based composite, as embodied by theinvention, the creep rates at 1200° C. and stresses greater than about70 MPa were high and led to premature failure of the sample. TheNb-silicide based composite could not support steady-state creep, andits microstructure was rapidly altered from primary to tertiary creepregime, and failed prematurely.

The creep data indicates that the Nb:(Hf+Ti) concentration ratio shouldbe maintained less than 5, and a Ti concentration should be kept below25%. At high Nb:(Hf+Ti) concentration ratios, hP16 Ti₅Si₃ type silicidecan be stabilized instead of tI32 Nb₅Si₃ type or tP32 Nb₃Si-typesilicides. These silicides have higher melting temperatures than eitherthe Ti₅Si₃ or the Hf₅Si3, and can lead to enhanced creep resistance inNb-silicide based composites. The creep performance can be sensitive tochanges in the constituent phases of the Nb-silicide based composite,and an intrinsic performance of the silicide or the (Nb). The creep ratealso indicates that a (Ti,Hf)₅Si₃ phase is detrimental to creepperformance, for example if the phase's [0001] direction is aligned witha loading axis of the creep sample or structural component. Creepdeformation in the Nb-silicide based composites was observed to occur byshear band formation in large-scale (Ti,Hf)₅Si₃ dendrites. HighNb:(Hf+Ti) concentration ratios can also reduce intrinsic creepperformance of a tetragonal silicide.

FIG. 3 illustrates creep rate as a function of percent of silicon in abase alloy. Low creep rates occur at 18% Si for any given stress. FIG. 4illustrates a plot of creep rate versus Nb:(Hf+Ti) for a Nb—16Si alloybase at 1200° C. and 140 MPa and illustrates the reduction in creep rateas the Nb:(Hf+Ti) concentration ratio is increased. Above aconcentration ratio of 3, the creep rate is no longer decreased, andthere may be no further creep benefits. Further, FIG. 5 is a plot ofcreep rate versus Nb:(Hf+Ti) for a Nb—16Si alloy base at 1200° C. and210 MPa. FIG. 6 is a plot of creep rate versus Nb:(Hf+Ti) for a Nb—16Sialloy base at 1200° C. and 280 MPa.

While various embodiments are described herein, it will be appreciatedfrom the specification that various combinations of elements, variationsor improvements therein may be made by those skilled in the art, and arewithin the scope of the invention.

What is claimed is:
 1. A niobium-based silicide composite exhibitingcreep resistance at temperatures equal to or greater than 1150° C., theniobium-based silicide composite comprising: at least silicon (Si),hafnium (Hf), titanium (Ti), niobium (Nb), and tin (Sn), wherein aconcentration ratio of Nb:(Hf+Ti) is equal to or greater than about 1.4and the niobium-based silicide composite exhibits a creep rate less thanabout 5×10⁻⁸s⁻¹ at temperatures up to about 1200° C. and at a stress ofabout 200 MPa.
 2. The composite according to claim 1, wherein theniobium-based silicide composite comprises a multiphase niobium andsilicide material.
 3. The composite according to claim 1, wherein theniobium-based silicide composite further comprises, in atomic percent,about up to about 25% titanium, silicon in a range from about 10 toabout 22%, hafnium (Hf) in a range from about 2% to about 8%, tin (Sn)in a range from about 0.2% to about 5%, and a balance niobium.
 4. Thecomposite according to claim 3, the niobium-based silicide compositefurther comprising, in atomic percent, up to about 10% tantalum (Ta), upto about 10% germanium (Ge), up to about 6% iron (Fe), up to about 8%boron (B), up to about 3% molybdenum (Mo), up to about 5% aluminum (Al),and one of chromium (Cr) up to about 15% and tungsten (W) up to about5%.
 5. The composite according to claim 4, wherein the amount of hafniumis, in atomic percent, about 4%.
 6. The composite according to claim 4,wherein chromium and tungsten are provided.
 7. The composite accordingto claim 1, wherein a concentration ratio Nb:(Hf+Ti) is in a range fromabout 1.4 to about 2.5.
 8. The composite according to claim 1, thecomposite comprising, in atomic percent, 7.5% hafnium (Hf), 16% silicon(Si), 21% titanium (Ti), and a balance niobium (Nb).
 9. The compositeaccording to claim 1, the composite comprising, in atomic percent, 8%hafnium (Hf), 16% silicon (Si), 21% titanium (Ti), and a balance niobium(Nb).
 10. The composite according to claim 1, the composite furthercomprising molybdenum (Mo), the composite comprising, in atomic percent,3% molybdenum (Mo), 8% hafnium (Hf), 16% silicon (Si), 25% titanium(Ti), and a balance niobium (Nb).
 11. The composite according to claim1, the composite further comprising molybdenum (Mo), the compositecomprising, in atomic percent, 9% molybdenum (Mo), 8% hafnium (Hf), 16%silicon (Si), 25% titanium (Ti), and a balance niobium (Nb).
 12. Aturbine component comprising the composite according to claim
 1. 13. Aturbine comprising the turbine component according to claim
 12. 14. Amethod of forming a niobium-based silicide composite, the compositeexhibiting creep resistance, the method of forming the compositecomprising: providing, in atomic percent, up to about 10% tantalum, upto about 10% geranium, tin in a range from about 0.2% to about 5%, up toabout 6% iron, up to about 8% boron, up to about 3% molybdenum, up toabout 5% aluminum, and one of up to about 15% chromium and up to about5% tungsten, a balance of niobium, wherein a ratio of Nb:(Hf+Ti) isequal to or greater than about 1.4.
 15. The method according to claim14, wherein the step of providing comprises providing, in atomicpercent, up to about 25% titanium, silicon in a range form about 10% toabout 22%, hafnium in a range from about 2% to about 8%, and a balanceof niobium.
 16. The method according to claim 14, wherein the amount ofhafnium is about 4% atomic.
 17. The method according to claim 14;wherein chromium and tungsten are provided.
 18. A turbine componentcomprising, in atomic percent, 7.5% hafnium (Hf), 16% silicon (Si), 21%titanium (Ti), tin (Sn) in a range from about 0.2% to about 5%, and abalance niobium (Nb).
 19. A turbine component comprising, in atomicpercent, 8% hafnium (Hf), 16% silicon (Si), 21% titanium (Ti), tin (Sn)in a range from about 0.2% to about 5%, and a balance niobium (Nb). 20.A turbine component comprising, in atomic percent, 3% molybdenum (Mo),8% hafnium (Hf), 16% silicon (Si), 25% titanium (Ti), tin (Sn) in arange from about 0.2% to about 5%, and a balance niobium (Nb).
 21. Aturbine component comprising, in atomic percent, 9% molybdenum (Mo), 8%hafnium (Hf), 16% silicon (Si), 25% titanium (Ti), tin (Sn) in a rangefrom about 0.2% to about 5%, and a balance niobium (Nb).
 22. Aniobium-based silicide composite exhibiting creep resistance attemperatures equal to or greater than 1150° C., the niobium-basedsilicide composite, in atomic percent, comprising: up to about 25%titanium, silicon in a range from about 10 to about 22%, hafnium (Hf) ina range from about 2% to about 8%, up to about 10% tantalum (Ta), up toabout 10% germanium (Ge), tin (Sn) in a range from about 0.2% to about5%,up to about 6% iron (Fe), up to about 8% boron (B), up to about 9%molybdenum (Mo), up to about 5% aluminum (Al), and one of chromium (Cr)up to about 15% and tungsten (W) up to about 5%, and a balance niobium.23. The composite according to claim 22, wherein the niobium-basedsilicide composite comprises a multiphase niobium and silicide material.24. The composite according to claim 22, wherein a concentration ratioof Nb:(Hf+Ti) is equal to or greater than about 1.4 and theniobium-based silicide composite exhibits a creep rate less than about5×10⁻⁸s⁻¹ at temperatures up to about 1200° C. and at a stress of about200 MPa.
 25. The composite according to claim 22, wherein the amount ofhafnium is, in atomic percent, about 4%.
 26. The composite according toclaim 22, wherein chromium and tungsten are provided.
 27. The compositeaccording to claim 22, wherein a concentration ratio Nb:(Hf+Ti) is in arange from about 1.4 to about 2.5.
 28. The composite according to claim22, the composite comprising, in atomic percent, 7.5% hafnium (Hf), 16%silicon (Si), 21% titanium (Ti), and a balance niobium (Nb).
 29. Thecomposite according to claim 22, the composite comprising, in atomicpercent, 8% hafnium (Hf), 16% silicon (Si), 21% titanium (Ti), and abalance niobium (Nb).
 30. The composite according to claim 22, thecomposite further comprising molybdenum (Mo), the composite comprising,in atomic percent, 3% molybdenum (Mo), 8% hafnium (Hf), 16% silicon(Si), 25% titanium (Ti), and a balance niobium (Nb).
 31. The compositeaccording to claim 22, the composite further comprising molybdenum (Mo),the composite comprising, in atomic percent, 9% molybdenum (Mo), 8%hafnium (Hf), 16% silicon (Si), 25% titanium (Ti), and a balance niobium(Nb).
 32. A turbine component comprising the composite according toclaim
 22. 33. A turbine comprising the turbine component according toclaim 32.